Removal of Mercury and Other Heavy Metals of Industrial and Contaminated Site Waste Waters by Organic Chelation, Coprecipitation, and High-Efficiency Particulate RemovalEPA Contract Number: 68D00241
Title: Removal of Mercury and Other Heavy Metals of Industrial and Contaminated Site Waste Waters by Organic Chelation, Coprecipitation, and High-Efficiency Particulate Removal
Investigators: Bloom, Nicolas S.
Current Investigators: Bloom, Nicolas S. , Hensman, Carl E.
Small Business: Frontier Geosciences Inc.
EPA Contact: Richards, April
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text | Recipients Lists
Research Category: Watersheds , SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
The Phase I objective is to investigate a new approach to the problem of trace metal removal from water. This new water treatment method relies on reactions long used by analytical chemists to obtain quantitative recoveries of trace metals from complex media. The method involves coprecipitation of the trace metal with a thiol-containing organic complexing agent such as aminopyrrolidine dithiocarbamic acid (APDC) or diphenylthiocarbazon (dithizon). These compounds are soluble as the alkali salts, but almost instantly form insoluble complexes with many transition metals, particularly Hg, Ag, Cu, Cd, Zn, Pb, Fe, and Ni. Thus, the reagent can be added to the aqueous sample in soluble form, and the trace metals can be filtered immediately or settled out. The method proposed will exhibit the following characteristics:
- Greater specificity for the removal of heavy metals (particularly Hg, Ag, Cu, Ni, Pb, and Cd) than are the currently popular ion exchange, activated carbon, and iron hydroxide precipitation methods. Common, yet benign, industrial matrices such as Ca, Mg, Na, and SO4 are inert with respect to the method proposed; therefore, it results in reduced reagent use, smaller sludge volumes, and higher extraction efficiencies.
- Although fine particulates are not effectively trapped by column methods such as ion exchange and activated carbon, the proposed method actually aids in the removal of fine particulates, which often carry a significant amount of the discharged trace metals loading.
- The proposed method utilizes an in situ solution-to-solid phase reaction, such that the extractive step is almost instantaneous, making rapid online treatment a feasible option. The often encountered kinetic problems related to diffusion from the aqueous phase to solid sorbants are avoided.
- The proposed complexing agents have extremely high binding constants with most transition group metals. Therefore, they will be able to not only extract the free and labile metal ions from solution, but also may extract the metals from many of the ambient chelators found in industrial effluents such as EDTA, NTA, citrate, and humic/fulvic acids. These ambient organometallic chelates often can render the metals unamenable to further treatment methods. If the proposed method works as anticipated, however, it will eliminate this problem.
Commercial opportunities for this technology include chlor alkali producers (Clorox, Ashta Chemical, Holtra-chem, Occidental Chemical, Canoxy, and Alcoa) and other parties (Bechtel Jacobs, SRS Westinghouse, Cominco Ltd., Exxon, and SpiritEnergy 76), who have expressed their specific interest in this technology.